Light emitting diode (LED) emits a light by converting an electric energy into an optical energy. After a current is applied to the LED, the current is diffused and infused to an epitaxial layer of the LED, and electrons and holes are combined to emit energy. Therefore, after electrons and holes are combined, energy will be emitted in the form of a light.
Currently in the semiconductor industries, reflector is normally formed of metal (such as silver) or indium tin oxide/distributed Bragg reflector (ITO/DBR) during the manufacturing process of flip-chip LEDs. When the reflector is formed of silver, the contact system is formed of metal, and therefore possesses the advantages of better current diffusion and lower operating voltage. However, when the reflector is operated under an ordinary current, the efficiency of light extraction of the silver reflector is not as good as the ITO/DBR reflector. When the reflector is formed of ITO/DBR, the reflector can have a reflectivity near 100% provided that ITO is used as an Ohm contact layer for diffusing the current. When operated under an ordinary current, in comparison to the silver reflector, the ITO/DBR reflector has a better performance in terms of reflectivity but a worse performance in terms of element voltage. On the other hand, when the reflector is operated under a large current (such as larger than 1 ampere), the silver reflector has better performance in terms of reflectivity. Therefore, it has become a prominent task for the industries to provide a semiconductor light-emitting structure having the advantages of both the silver reflector and the ITO/DBR reflector.